Developing low-cost and high-efficiency g-C3N4 (CN) semiconductor with modification has been proved to possess the potential advantage for environmental remediation in recent years. Herein, element doping of CN framework was found significantly on controlling its electronic structure. The new two-dimensional photocatalyst of Co-doped CN (Co-CN) applicable in photocatalytic reactions for 2-Mercaptobenzothiazole degradation was designed and synthesized. It was for the fast time revealed that the Co-N bonding could lead to enhance significantly photoelectric properties, the rate for electron-hole pairs separation and photocatalytic activity in comparison with bulk CN. The characterization and density functional theory (DFT) results insight into the reason that the 3d electrons of the doped Co has excellent contribution to adjust the band gap of Co-CN. The present work provide a broadening window for Metal-doped CN with outstanding performance.